Mass data storage devices have begun to be used in applications outside of personal computers. In some applications, especially in the consumer electronics area, there is a desire to make the storage device secure such that the device cannot be accessed by a host other than the host initially shipped with the device.
One way to make a storage device secure is to use a cryptographic algorithm that relies on a secret quantity such as a password or cryptographic key. Such algorithms are typically open to the public and as such rely heavily on the secret quantity. The strength of the secret quantity is a function of how easy it is to guess the quantity. In general, the strongest secret quantity will be one that is selected through a true random process, such as random number generation.
In current disc drives, random numbers are generated by means of a set of internal timers. In particular, the values produced by these timers are sampled at some point in time based on some algorithm. The sampled values are used to form the random number. Unfortunately, numbers produced in this manner are not truly random and in fact it has been found that the same number is likely to be generated twice using the existing system. In addition, if the algorithm becomes known, the numbers produced by prior art drives can be guessed based on the nominal clock speed of the disc drive processor.
As such, a mechanism is needed to generate true random numbers in a data receiver such as a read channel in a disc drive.